Kato Takuma, Tatematsu Ryo, Nakao Kenichi, Inomata Tomohiko, Ozawa Tomohiro, Masuda Hideki
Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan.
Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan.
Inorg Chem. 2021 Jun 7;60(11):7670-7679. doi: 10.1021/acs.inorgchem.0c03657. Epub 2021 May 6.
We previously reported the preparation and characterization of a Ni(II) complex capable of electrocatalytic hydrogen generation. The complex [Ni()Cl]Cl () includes a 6-((diphenylphosphino)methyl)pyridin-2-amine ligand (), which has an amino group as a base that acts as a proton transfer site by virtue of its location near the metal center. In order to study the effect of counteranions in hydrogen generation, two additional Ni() complexes with weakly coordinating/noncoordinating counteranions, Ni() (OTs = -toluenesulfonate) () and Ni() (), were synthesized. Their X-ray crystal structures reveal that the Ni(II) ion is coordinated with two bidentate ligands in both complexes. Complex contains both and isomers in the unit cell. The former is in an axially elongated square-pyramidal geometry (τ = 0.17), and the latter is in a nearly square planar geometry (τ = 0.11) with two weakly interacting OTs anions at the axial sites. Complex has only the isomer in the solid state, which is in a nearly square planar geometry (τ = 0.10). These complexes are slightly different from , which has a distorted-square-pyramidal geometry (τ = 0.25) with a coordinated chloride anion. UV-vis spectra of and in MeCN show a spectral pattern characteristic of a square-planar Ni(II) complex. These spectra are slightly different from the unique spectrum of , which is typical of an axially coordinating Ni(II) species as a result of having a Cl anion at the apical position. Electrocatalytic hydrogen generation promoted by these three Ni(II) complexes (1.0 mmol) demonstrates an increase in the catalytic current induced by stepwise addition of HOAc (p = 22.3 in MeCN) as a proton source. The complexes demonstrate turnover frequencies (TOF) of 3800 s for , 5400 s for , and 8800 s for in MeCN (3 mL) containing 0.1 M -BuN in the presence of HOAc (145 equiv) at overpotentials of ca. 530, 490, and 430 mV, respectively.
我们之前报道了一种能够进行电催化产氢的镍（II）配合物的制备与表征。配合物[Ni()Cl]Cl（）包含一个6 - （（二苯基膦基）甲基）吡啶 - 2 - 胺配体（），该配体具有一个氨基作为碱，由于其靠近金属中心的位置而充当质子转移位点。为了研究抗衡阴离子对产氢的影响，合成了另外两种带有弱配位/非配位抗衡阴离子的镍（）配合物，Ni()（OTs = - 甲苯磺酸盐）（）和Ni()（）。它们的X射线晶体结构表明，在这两种配合物中镍（II）离子均与两个双齿配体配位。配合物在晶胞中同时包含和异构体。前者呈轴向拉长的四方锥几何构型（τ = 0.17），后者呈近乎平面正方形几何构型（τ = 0.11），在轴向位置有两个弱相互作用的OTs阴离子。配合物在固态时仅具有异构体，呈近乎平面正方形几何构型（τ = 0.10）。这些配合物与具有扭曲四方锥几何构型（τ = 0.25）且带有配位氯离子的有所不同。和在乙腈中的紫外 - 可见光谱显示出平面正方形镍（II）配合物的特征光谱模式。这些光谱与的独特光谱略有不同，由于在顶端位置有一个Cl阴离子，的光谱是轴向配位镍（II）物种的典型光谱。这三种镍（II）配合物（1.0 mmol）促进的电催化产氢表明，作为质子源逐步加入HOAc（在乙腈中p = 22.3）会导致催化电流增加。在含有0.1 M -BuN的乙腈（3 mL）中，在HOAc（145当量）存在下，配合物在过电位分别约为530、490和430 mV时的周转频率（TOF），对于为3800 s，对于为5400 s，对于为8800 s。
